An Inexpensive Kugelrohr Still Bulb-to-bulb, or Kugelrohr, distillation has became a popular means for the simple distillation of minute quantities (1.5 mg) of volatile materials, either at atmospheric pressure or under vacuum. We have seen commercial units costing hundreds of dollars, and elaborate homemade models. The least expensive unit an the market costs less than $100, but requires a Variac for operation, the costs of which doubles its effective price. We wish to describe a simple unit which is superior to some commercial units, and may he assembled for a small fraction of the price. The key to the unit is a variable temperature air bath whose temperature can be easily controlled and monitored. We have found that eommereisllv availahle "toaster-ovens" suit the . ouroose heautifully. Although these units are available a t retail in a variety of models, almost any of which will do, it is often possible to purchase a used oven a t a yard sale for $10 or so. Most units have a thermostatted temperature control, hut we have f w n d it useful to install a thermometer through the top of the oven using a small collar and rubber o-ring as well. A 2-in, h d e is cut into the side of the oven to accommodate a flask up to50 ml. It may be necessary toremove some of the front door hinging mechanism at this point, depending on what model is used. We have used two hinged metal plates with a smaller hale drilled a t the center to fit closely around the neck of the flask (see illustration). Even though some commercial units employ a rocking motor to prevent humping, and one may he added to this unit, we have found additional spacing bulbs, inside the oven, to be sufficient to insure a cleandistillation. To cool the collecting bulb outside the oven, aslaw dropwise stream of methylene chloride on a tissue wrapped around the hulb is quite efficient. A serendipitaus advantage of this unit over a,mmercially availahle models is that the glass front permits viewing the progress of the distillation.
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Wayne C. Guida Eekerd College St. Petersburg, F L
554 I Journal of Chemical Education
Robert E. Gawley University of Miami Coral Gahles, FL33124
